In many electrical systems a load is connected to a source through a switching power converter. It is advantageous to know how the actions of the load affect the power strain on the incoming source. For example, knowledge of the regulator input power is typically used for telemetry purposes, fault monitoring and system optimization. The power required from the source equals that consumed by the load plus losses within the switching power converter. If there is no loss between the source and the power converter, the power demanded from the source equals the input power to the converter. Input voltage to a converter is an existing measurement required for protection and possibly control of the converter. Then, only input current must be known to obtain the input power of the power converter. Obtaining the input current value is considerably more involved than voltage measurement if accuracy is to be maintained without adversely affecting efficiency. In addition, obtaining the input current generally requires the addition of a series element such as a sense resistor in order to obtain a measurement of the current through the series element.
Input power is the product of input voltage and input current. Input voltage is an existing telemetry value required for power supply protection and control. Input current is measured or estimated. In the case of measurement, external components are required on the board, increasing cost and board area consumed. In terms of estimation, the input current estimate relies heavily on the accuracy of the sensed input voltage. The input voltage rail is typically noisy which leads to incorrect current estimation and incorrect input voltage reporting. A combination of erroneous current and voltage estimates results in erroneous input power reporting. Hence, a more accurate switching voltage regulator input power estimation technique is desirable.